Since replacing my V-6's water pump, thermostat, all hoses, radiator & cap, my car has been running great here in hot, southern california.

Yesterday, I took it in for an oil change. When I got home, I wanted to check up on the work done by the mechanics. The engine was cold. The overflow tank was nearly full. That seemed curious. Did the Toyota people overfill it.

So, I thought it best to check coolant level in the radiator. When I opened the radiator cap, it made a strong sucking noise and the overflow tank burbled a bit. The coolant in the radiator was low. It took 13 squirts from a turkey baster to get the level to the top.

As I said, the engine has been running fine. Why would there be excess coolant in the overflow and not enough in the radiator?

 

Could be the radiator cap, it is supposed to flow both ways allowing the coolant to flow in and out.

Check the hose between the radiator and overflow tank for plugging.

 

I've been living with this hidden gremlin now for about 3 months. Losing about .5 qt - 1 qt of coolant over a few weeks. Temperatures have been in the low '70s here in Southern California.

Yesterday I bought a new radiator cap from Toyota.($30---ouch). On a 10-mile drive today, the temp gauge appeared to be a bit lower after the engine warmed up. My old thermostat appeared to run a tad colder. The parts guy at Toyota said he sells a lot of radiator caps. They don't seal properly after awhile.

I'll report back in a month about the coolant loss.

 

Thanks for the update.

 

Three weeks has passed since I replaced the radiator cap. Problem solved. No more depletion of coolant in the system or overflow tank.

At a cost of $30. Hey, I'm happy.

 

Choose the correct pressure cap for your car.

 

The parts dept at the Toyota shop pulled up the VIN number on my car and selected the cap. I never knew there were different specs on caps for the same car.

If it makes any difference, I live right at Sea Level. After about 6 weeks of operation, the coolant level in the system and overflow tank hasn't changed by one drop.